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Description of four physical cleaning methods for electromagnetic flowmeter electrodes

First, electrochemical method

The electromagnetic flowmeter metal electrode has an electrochemical phenomenon in the electrolyte fluid. According to the electrochemical principle, the electrode has a contact electric field with the fluid, and the contact of the electrode with the fluid is caused by the electric double layer existing between the electrode fluids. The study of the electric field of contact between the electrode and the fluid reveals that the molecules, atoms or ions of the substance have an enrichment or a poor adsorption at the interface, and it is found that most of the inorganic anions are surface active substances, which have a typical ion adsorption law, while the surface of the inorganic cation Very little activity. Therefore, the electrochemical cleaning electrode only considers the case of anion adsorption. The adsorption of anions is closely related to the electrode potential. The adsorption mainly occurs in the potential range which is more positive than the zero charge potential, that is, the surface of the electrode with a different charge. On the surface of the electrode with the same charge, when the residual charge density is slightly larger, the electrostatic repulsion is greater than the adsorption force, and the anion is quickly desorbed, which is the principle of electrochemical cleaning.

Second, mechanical removal method

The mechanical cleaning method achieves electrode removal by installing a special mechanical structure on the electrodes of the electromagnetic flowmeter. There are currently two forms: one is the use of a mechanical scraper. A scraper with a thin shaft is made of stainless steel, the scraper is taken out through the hollow electrode, and a mechanical seal is used between the thin shaft and the hollow electrode to prevent the outflow of the medium, thus forming a mechanical scraper. When the thin shaft is rotated from the outside, the blade is rotated against the plane of the electrode end to scrape off the dirt. This type of scraper can be manually or automatically driven by a motor driven fine shaft. The other is to install a wire brush for removing dirt in the tubular electrode, and the shaft is wrapped in a sealed "O" ring to prevent fluid leakage. This type of cleaning device requires someone to pull the wire brush to clean the electrode, which is not very convenient to operate.

Third, ultrasonic cleaning method

The ultrasonic voltage of 45~65 kHz generated by the ultrasonic generator is applied to the electrode of the electromagnetic flowmeter, so that the energy of the ultrasonic wave is concentrated on the contact surface of the electrode and the medium, thereby utilizing the ability of the ultrasonic wave to crush the dirt to achieve the purpose of cleaning.

Fourth, electric breakdown

This method is periodically applied between the electrode of the electromagnetic flowmeter and the medium using AC high voltage, generally 30~100V. Since the electrode of the electromagnetic flowmeter is attached, the surface contact resistance becomes large, and the applied voltage is almost concentrated on the deposit, and the high voltage will break down the deposit and then be washed away by the fluid. From the safety point of view, the electric breakdown method must be used to clean the AC high voltage directly on the sensor signal output terminal when the flowmeter interrupts the measurement work, the signal line between the sensor and the converter is disconnected, and the power is off.

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